This invention relates generally to filling a container with material, and more particularly concerns a butterfly valve for controlling the flow of powders such as toner from a fill tube to a toner container.
Currently when filling powders, for example, toners into toner containers, toner is transported from the toner supply hopper into the container by a rotating auger. The auger is a spiral shaped mechanical part which pushes particles of toner inside a fill tube by direct mechanical contact. The speed of the toner movement in the fill tube is proportional to the speed of rotation of the auger and is limited by heat release due to auger/toner friction. High auger speed will cause the toner to melt, particularly for low melt toner such as disclosed in U.S. Pat. No. 5,227,460 to Mahabadi et al. The relevant portions thereof are incorporated herein by reference.
The problems associated with controlling the filling of toner containers are due primarily to the properties of the toner. Toner is the image-forming material in a developer which when deposited by the field of an electrostatic charge becomes the visible record. There are two different types of developing systems known as one-component and two-component systems.
In one-component developing systems, the developer material is toner made of particles of magnetic material, usually iron, embedded in a black plastic resin. The iron enables the toner to be magnetically charged. In two-component systems, the developer material is comprised of toner which consists of small polymer or resin particles and a color agent, and carrier which consists of roughly spherical particles or beads usually made of steel. An electrostatic charge between the toner and the carrier bead causes the toner to cling to the carrier in the development process. Control of the flow of these small, abrasive and easily charged particles is very difficult.
The one-component and two-component systems utilize toner that is very difficult to flow. This is particularly true of the toner used in two-component systems, but also for toner for single-component systems. The toner tends to cake and bridge within the hopper. This limits the flow of toner through the small tubes which are required for addition of the toner through the opening of the toner container. Also, this tendency to cake and bridge may cause air gaps to form in the container resulting in partial filling of the container.
In addition, during the cartridge filling process, the toner fillers need to be periodically replenished with new toner. The toner bin usually positioned above the fillers hopper and equipped with an on/off butterfly valve that opens and closes the flow. The butterfly valve consists of a flat disc, which can rotate (usually up to 90 degree) inside a short pipe serving as a valve housing. The diameter of the disc is slightly smaller then inside diameter (ID) of the housing/pipe. The disc is turned by an electrical or pneumatic actuator, located on the outer surface of the valve and connected to the disc by a short axle. During the cartridge toner filling process, the toner in the filling machine hopper is periodically (every several minutes) replenished. During the valve actuation, the valve disc moves against the seal causing the seal to compress. The seal prevents toner from bypassing the disc when it is in the closed position.
A problem with the above type butterfly valve is that the toner particles in the area between the disc and the seal are compressed/damaged when the butterfly valve switches states between the on/off position. Applicants have found that the compressed/damage toner particles lead to print defects when used in xerographic printing machines. Various attempts have been used to minimize the compression zone—inflatable-seals, smaller seals, different seal material and smaller discs but these have not been successful.
The present invention obviates the problems noted by providing minimal-compression butterfly valve that employs a novel seal and disc arrangement that creates an effective sealing-effect without creating the deleterious toner compression-zone.
In an embodiment of the present disclosure there is provided a butterfly-type valve for controlling toner material flow to a toner container, comprising a valve plate which is pivotally disposed in an elongate flow path defined by a passage way, wherein the valve plate is pivotal from a closed position which substantially closes a fluid communication along the path to an open position which maximally permitting fluid communication along the path, a gap area defined between said valve plate and said passage way when said valve plate is in said closed position which allows minimum toner material flow there through without compressing the toner material, and a pump for supplying vacuum to said gap area when said valve plate is in said closed position to stop said minimum toner material flow.